As best we can tell, she must have been going through some kind of developmental growth spurt. New neural connection apparently take a lot out of a baby. We've seen some improvement in a couple of areas--things she'd already been doing sometimes that she now does all the time. In particular, her vision seems to have had a big jump. She loves stripes and other bold patterns, even when they're not black and white. She can track objects easily, both with her head and with her eyes alone. She seems to be able to see us from a longer distance than she could before, and she can definitely see when we're smiling at her. Her motor skills are also improving, though not as dramatically. She is still working on keeping her head up. She desperately wants more head control. Head control = baby freedom! All of this is boosted by increasing periods of alert wakefulness. She is now awake long enough that I've started to think of her as napping when she sleeps--before, she just slept all the time.
She's also grown. A lot. She's clearly turning all that milk into more baby. She's long and lean--like a string bean. A string bean with GIGANTIC feet.